(1) Field of the Invention
The present invention relates to a connection head of a fuel line for use in a connection assembly used in a high pressure fuel system. In particular, the present invention relates to a connection head of a fuel line having a spherical outer surface with a liner. The present invention also relates to a method of forming a connection head having a spherical shape for use in a high pressure fuel system.
(2) Description of the Related Art
High pressure fuel lines are used in high pressure fuel systems to connect the various components of the system together. The connection head on the end of the fuel line is seated against the seating surface in the connection stub of the component. The fuel line is secured in place on the connection stub by a lock nut which applies a force to the connection head of the fuel line and moves the connection head into sealing connection against the seating surface of the connection stub of the component.
To reduce stress induced in the fuel line caused by the misalignment of the connection head of the fuel line and the seating surface of the connection stub of the fuel system component and to maintain the integrity of the sealing connection, connection assemblies for high pressure applications, such as high pressure fuel systems, use fuel lines having a connection head with a spherical shape. The connection head of the fuel line mates with the conical or curved sealing surface of the connection stub of the component of the fuel system to form a seal. The spherical shape of the connection head also allows for easier assembly of the connection assembly when there is misalignment between the fuel line and the fuel system component. Connection assemblies for high pressure fuel systems which use fuel lines having an end fitting having a spherical shape are described in U.S. Pat. No. 6,497,220 to Boecking and U.S. Patent Application No. 2006/0284421 to Fonville et al.
However, in the past, the connection head having the spherical shape was constructed by securing an end fitting having a spherical outer surface to the end of the fuel pipe. The end fitting was secured onto the fuel pipe by brazing or crimping. However, the attachment of the end fitting on the outside of the fuel line creates a join which is capable of become separated due to stress or misalignment and thus creates the potential for a leak in the fuel line. U.S. Pat. No. 3,449,937 to Dimmig shows a high pressure fuel line head formed by a two-slip cold forming process. However, this invention uses a heavy walled tube to form the spherical head. U.S. Pat. No. 5,997,050 to Fleckenstein et al. shows the use of cold forming to form a double cone coupling nipple formed in a relatively thin-walled steel tube. However, the conical area of the nipple has a wall thickness approximately double of the thickness of the remaining tube.
The related art has shown sealing ends or sealing heads which are formed with a continuous outer surface and which have an inner support ring or a filler ring in the inside of a sealing end or sealing head. Illustrative are U.S. Pat. No. 2,497,441 to Detweiler; U.S. Pat. No. 3,698,745 to Mundt; U.S. Pat. No. 4,029,345 to Romanelli; and U.S. Pat. No. 5,109,888 to Usui.
Detweiler describes couplings for use with pipes or hydraulic lines where a flare or bead is provided on the end part of the tubing which is inserted into the coupling body. When the bead is formed, an annular recess is left within the tubing. A filler ring is provided on the inside of the tubing within the recess. The filler ring fills the recess so that the internal surface of the filler ring is cylindrical and flush with the internal surface of the tubing.
Mundt describes an inverted flare type hose coupling having a conically shaped eyelet wall end supported against the sealing forces by a support ring. The exterior of the support ring includes a conical or tapered surface truncated by the radial end face of the outer end. The wall end does not extend over the radial end face of the outer end of the support ring. The support ring may include a cylindrical axial extension which internally supports the eyelet alignment portion.
Romanelli describes a pipe having a flanged and shanked seal ring inserted in the end portion. The seal ring includes a stem and a flanged head. The flanged head of the seal ring does not extend into the pipe.
Usui describes a high pressure metallic pipe having a connecting head with a flat and smooth inner peripheral surface. To form the pipe, a steel pipe of a large wall thickness is used. A sleeve washer is attached near the connecting end, and the end of the pipe is radially expanded outwardly using a mandrel member. The metallic ring is buried inside the radially expanded pipe. The cross section of the metallic ring may be semicircular, triangular or trapezoidal. Once the ring is in position, the peripheral wall of the radially expanded tube is pressed inwardly using a punch member having a die conforming to the contour of a head to form the head having the shape of a truncated cone. The metallic ring is buried in the annular groove formed in the inner peripheral surface of the pipe during the formation of the head. The metallic ring fills the annular groove so that the connecting head has a flat and smooth inner peripheral surface.
Also of interest are U.S. Pat. No. 6,981,722 to Watanabe and U.S. Pat. Application Publication No. 2007/0006848 to Ricco et al. which show connection assemblies for high pressure fuel systems.
Only of minimal interest is U.S. Pat. No. 4,669,761 to Ruling which shows a fitting for a pressurized fuel line which uses an expander inside the end of the tube to force the end of the tube against the fitting member in a very tight seal.
There remains the need for a connection head for a high pressure fuel line having a spherical shape where the outer surface of the fuel line is continuous and a liner is provided inside the connection head and for a method of forming the connection head, which is economical and eliminates the step of brazing or crimping.